A telescope is an optical instrument that aids in the observation of remote objects by collecting electromagnetic radiation (such as visible light). The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s, by using glass lenses. They found use in both terrestrial applications and astronomy.

A periscope...

A telescope is an optical instrument that aids in the observation of remote objects by collecting electromagnetic radiation (such as visible light). The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s, by using glass lenses. They found use in both terrestrial applications and astronomy.

A periscope is an instrument for observation over, around or through an object, obstacle or condition that prevents direct line-of-sight observation from an observer's current position.

Galileo telescope or a spyglass is a telescopic monocular optical instrument intended to obtain a close-up view of distant objects.